In connecting a module to a printed circuit board or the mother board of an electric appliance, a connector shall be used. FIG. 1 illustrates a conventional connector for this purpose. As illustrated, the connector (2) has a channel (23) in longitudinal direction, which receives the module (1) to be connected, pairs of contacts bilaterally fastened inside the casing (21) thereof, which hold the module (1) in place and have each a tail (24) extended out of the casing (21), and two guide posts (22) projecting downwards on two opposite ends thereof. By inserting the guide posts (22) and the tails (24) of all contacts in respective holes on the printed circuit board, the connector (2) is connected in place. Once the module was inserted in the channel (23), the printed terminals (11) on the module (1) become respectively connected to the contacts of the connect (2), and therefore the module is electrically connected to the printed circuit board. Examples of the conventional contacts are shown in FIGS. 2 and 3. FIG. 2 illustrates a pair of first contacts (3) each having a clamping portion formed on its top portion. FIG. 3 illustrates a pair of second contacts 4 each having a clamping portion formed on its bottom portion. The first contacts (3) and the second contacts (4) are alternatively arranged in rows. Once the module (1) has been inserted in the channel (23), the paris of first contacts (3) clamp the upper part of the module (1) inside the channel (23), and the pairs of second contacts (4) clamp the lower part of the module (1) inside the channel (23), and therefore the module (1) becomes firmly retained in place and electrically connected to the printed circuit board below. As illustrated in FIG. 2, each first contact (3) is comprised of a tail (32) on the bottom end thereof connected to the printed circuit board below, a clamping portion (31) formed on an upper portion of the contacts having a stop end 34 formed on the top portion of the contact 3, and a supporting portion (33) on the middle between the tail (32) and the clamping portion (31). The supporting portion (33) has an upper portion obliquely extended upwards inwards towards the clamping portion (31) and a lower part obliquely extended downwards inwards, when positioned on the right side, or downwards outwards, when positioned on the left side, towards the tail (32) connected to a respective contact on the printed circuit below the connector. When assembled, the tail (32) is extended out of the bottom edge of the casing (21), the supporting portion (33) is stopped against the inside surface of the casing (21), the stop end (34) is stopped against a respective inside flange (23A) in the channel (23), and the clamping portion (31) projects into the channel (23). Once the module (1) was inserted into the channel (23), the clamping portion (31) is squeezed outwards causing each first contact (3) to produce a stress for firmly clamping the module (1) between the two contacts 3. Because each first contact (3) is simply supported in place at two bearing points, namely, the supporting portion (33) and the stop end (34), it may be displaced easily. More particularly, the free stop end (34) may be disconnected from the respective inside flange (23A) (see the dotted lines in FIG. 2). As illustrated in FIG. 3, each second contact (4) is comprised of a tail (42) on the bottom end thereof connected to the printed circuit board below the connector, a clamping portion (41) on the top end thereof projected into the channel (23), and a supporting portion (43) on the middle between the tail (42) and the clamping portion (41). The supporting portion (43) has an upper portion formed into a bend (44) obliquely extended downwards to connect the clamping portion (41) at a lower central end thereof, and a lower portion obliquely extended downwards inwards, when positioned on the right side, or downwards outwards, when positioned on the left side, and to connect the tail (42) connected to a respective contact on the printed circuit below the connector. Because a large angle is formed between the bend (44) and the clamping portion (41) and projected into the channel (23), the clamping portion (41) may be bent outwards (see the dotted lines in FIG. 3) or even broken when the module (1) was inserted into the channel (23). Similar to the first contacts (3), each second contact (4) is unstably supported in place at two bearing points, namely, the bend (44) and the supporting portion (43). In this structure of connector, the pitch between two adjacent contacts is about 0.3 m/m to 0.5 m/m. Therefore, residual tin solder (33;43) may be gathered around the tails (32;42) during the process of tin soldering, causing a short circuit across every two adjacent contacts 3, 4 (see FIG. 6). Still another disadvantage of this structure of connector (22) is that the guide posts (22) which are each integrally formed on the plastic casing (21), which may be broken easily during the installation of the connector.